Valve tappet



Oct 30, 1928.

An W. POPE, JR

VALVE. TAPPET Filed March 12, 1925 MAMA W KKK g: 5 2 f/ 0 E J J J Patented Oct. 30, 1928.

UNITED STATES PATENT OFFICE.

ARTHUR w. POPE, an, or WAUKESI-IA, WISCONSIN, ASSIGNOR T0 WAUKESHA oron COMPANY, or WAUKESHA, WISCONSIN, A CORPORATION or wIscoNsINI VALVE TAPPET.

Application filed March 12, 1925.

My invention relates to valve tappets which are usually placed between the cam shaft of an explosive engine and the several controlling valves to communicate the various cam movements to the valves. These tappets are usually adjustable and are set when the motor is cold, the setting being usually made to keep the clearance between the tappet and the valve and cam at a minimum, but at the same time permitting the valves to properly function. However, the engine frame and the valves are usually of different material having different co-eflicients of expansion, and when the engine heats up the difference in expansion will disturb the clearance adjustment and the valve operation may become noisy or may be interfered with. The tappet structure itself also responds to temperature changes and so afl'ects clearance adjustment. Consider, for example, an engine structure in which the case is of aluminum whose co-efiicient of expansion is very much greater than that of steel, of which the valves are usually made. In such combination the great difference in expansion will cause such increase in the clearance that the valve operation will become very nois L Where the engine frame and valves are of materials whose co-eflicients of expansion do not differ to any great degree, the tappet structure might respond sufliciently to temperature change to affect the clearance setting. In the case of an exhaust valve, where the valve structure will be subjected to very high heat, the valve structure may expand at a greater rate than the surroundingengine frame, and in such situations the tappet structure would, not properly controlled, interfere with the proper operation of the valve.

The important object of my invention is to produce a tappet structure capable of automatically adjusting its length under temperature variations to compensate for the difference" of expansion rate of the engine frame and valve, and at the same time compensating for its own change under temperature variations, so that the most efiicient clearance between the tappet and valve will be maintained at all times. In accordance with my invention, the tappet structure, between its cam abutment and its valve abutment;- end, has interposed a number of layers or sleeves of metal of comparatively high coefficient of expansion,- and these layers are so intercon- Serial No. 15,092.

nectcd that their expansions will be algebraically accumulated to thus cause the tappet structure as a whole to increase or decrease its length to thus compensate for the different expansion of the engine frame and valve, and keep the proper clearance under all conditions.

In the accompanying drawings: 1 Figure is a vertical sectional view of parts of an engine structure showing avalve, the camshaft, and the interposed valve tappet;

Fig. 2 is an enlarged vertical sectional view of the tappet structure; and

Flgs. 3, 4, 5 and 6 diagrammatically represent various combinations of compensating members. The frame 10 is shown supporting the cylmder 11, the valve frame work 12, and the cam shaft 13. The intake valve 14, as shown, controls the connection of the intake passageway 15 with the cylinder, the valve normally seating on the seat 16. The valve stem 17 extends downwardly and is slidable in the bushing 18 supported in the frame work 12, and at its lower end the stem. supports the annular cup 19 for seating the compression spring 20, which at its upper end abuts against the frame work 12, the spring thus tending to hold the valve 14 on its seat.

The tappet structure T is of cylindrical form and has vertical reciprocation in the sleeve 21 suitably supported from the frame 10. The detail construction of one form of tappet structure is clearly shown in Fig. 2. The body 22 is a tubular shell and at its lower end has the abutment base 23. The tappet structure is in vertical axial alignment with the valve and with its base 23 in the path of a cam 24 of the cam shaft 13. The body of the tappet structure is preferably of steel and Within the cylindrical tubular part 22 is the tube or sleeve 23 of some metal, such as aluminum,'which has a much higher co-efiicient of expansion than steel. Within the tube 23 is a tube 24 of steel, which has the external lateral flange 25 at its upper end overhanging the upper end of the aluminum sleeve 23, and at its lower end the tube 24 has the inwardly extending annular flange 26. An inner tube or sleeve 27 of metal, such as aluminum, seats on the flange 26 and extends upwardly beyond the upper end of the tube 24, Where it has the expanded top 28 forming a seat for the abutment screw 29, which threads into the tube 27 By means of the screw 29 the length of the tappet and the tween the tappet structure head and the valve but the adjusted clearance willtincrcase as soon as the engine heats up, owing to the difference between the expansion rate of the engine frame and that of the valve, and the clearance between the tappet and the valves may become great enough to cause noisy operation. With my improved tappet structure this can be eliminated. As soon asthe structure is heated, the various tubes will expand, the aluminum tubes expanding to a greater extent than the steel tubes. The outer aluminum tube 23 will first expand or elongate, and on account of its engagement with the outer flange 25 of the steel tube 24, this steel tube will be shiftedoutwardly bodily. The steel tube 24 also expands, but not as much as the aluminum tube 23, so that the resultant movement will be a bodily outward movement of the steel tube. As the inner flange 26 of the steel tube engages against the inner end of the inner aluminum tube 27, such inner aluminum tube will be bodily shifted outwardly with the steel tube 24 as this tube is shifted outwardly by the outer aluminum tube23. In addition to this bodily outward movement of the inner tub'e, such tube will also"-''xpand. Thus the steel tube 24 serves as a connection for adding the expansion of l the inner aluminum tube 27 to that of the outer aluminum tube 23, and the total expansion or the elongation of the tappet structure will be the expansion or elongation of the outer aluminum tube plus that of the inner aluminum tube, less the expansion or elongation of the steel tube 24. As the expansion co-efiicient of aluminum is considerably greater than that of steel, the tappet structure will have considerable expansion or elongation, and such expansion or elongation is sufficient to permit the tappet structure to follow the expansion of the engine frame and maintain a substantially constant and noiseless clearance between the tappet structure and the valve. The tubes or sleeves of the tappet structure fit each other snugly enough to prevent any loose or noisy motion, but their engagement is sutliciently yielding to permit them to return to normal position after a heating or expansion. The natural hammer valves will return the tubes to their normal position as the tappet structure and frame parts cool off.

In Fig. 3 I diagrammatically show the arrangement of Fig. 2. The expansion tappet comprises the two aluminum bars A and the steel bar or tube B interposed. between the cam gear 24 and the valve stem 17. This arrangement will give a large expansion of the tappet structure which would be very desirable where the engine frame is of some material, such as aluminum, and the valve of steel with the co-eflicicnt of expansion of aluminum much greater than that of steel. Suppose, for example, that the rate of expansion of aluminum is twice that of steel and that the unit of expansion of steel is one. Each of the aluminum members in Fig. 3 would then tend to increase the length of the tappet unit by two units and both aluminum elements would tend to increase the length by four units. The steel members would expand to the extent of one unit, but in a direction which would tend to decrease the length of the tappet structure, so that consequently summing up algebraically the total elongation or expansion of the tappet structure would be three units.

In cases where the materials do not differ much in their expansion as, for. example,

where the engine case is cast iron and the valve of steel, the response of the tappet unit to heat would be the vital factor in maintaining proper clearance and permitting proper operation of the valve. In other words, where the material of the frame and the valve have the same co-eflicient of expansion, the. valve tappet should remain of constant length. In Fig. 4 I have shown an arrangement for accomplishing this. Here the two steel members B tend to increase the length of the tappet structure by two units, while the aluminum member A will tend to reduce the length by two units, so that the aluminum expansion neutralizes the steel expansion and the length of the tappet structure will not be changed. If the tappet structure were entirely of steel under the condition mentioned, it would expand under heat and perhaps pre vent proper closure of the valve.

In some cases it may be necessary for the tappet structure to reduce its length under heat in order to maintain proper clearance and permit proper functioning of the valve. This might be true where the frame is of cast iron or steel and the valve of steel, but the valve controlling the exhaust passageway and subjected to exceptionally great heat, so that the valve would expand more than the surrounding frame. An arrangement like that shown in Fig. 5 would take care or" a situation like this. The three steel expansion members B will tend to expand the tappet structure, each by one unit, or together by three units, and the two aluminum members A would each llu tend to decrease the length by two units, or together by four units, the alegebraic resultant of the movement causing a contraction by one unit of the tappet structure and such contraction would compensate for the expansion or increased length of the exhaust valve relative to the frame.

Fig. 6 diagrammatically shows the steel body part 22 of the structure of Fig. 2, but with only a single aluminum expansion member A. therein and with this arrangement the entire expansion of the aluminum member would be available for compensating purposes.

Thus, by use of different materials of proper length and proper arrangement, a tappet structure can be built up which will compensate for and neutralize the various difierences in expansion which might otherwise disturb the clearance or valve operation and adjustment.

The tappet structure disclosed is very simple and inexpensive, yet highly efficient in automatically keeping the tappet clearance within proper limits to prevent noisy operation of the engine while permitting proper functioning of the valves.

Having described my invention, what I claim is as follows:

A valve tappet comprising an outer tubular member, a first tubular member within said outer member, a second tubular member with-' in the first member, and a third member within the, second tubular member, said first member bearing at one end on the outer member and said .second member hearing at one end 7 

